Starting a gas turbine aircraft engine on the ground with a sensorless brushless starter-generator typically involves sending a predetermined sequence of current signals to the windings of the stator to cause the rotor magnets to begin to rotate in accordance with the predetermined sequence of current signals provided to the corresponding windings of the stator. Since the rotor position is not known, a trial and error approach is typically used, wherein a rotor position is assumed and current provided to the stator based on the assumed position and, if starting is not successful, a different rotor position is assumed, and the process is repeated, until starting occurs.
As difficult as this is, in applications such as a turbofan or turboprop where the rotor of the starter-generator may already be rotating as a result of ground airflow through the engine, trial and error starting becomes even more difficult. Therefore, there is a need for improvement.